Dengue Fever

Introduction

Dengue (DENG-gey) fever is a mosquito-borne disease that occurs in tropical and subtropical areas of the world. Over half of WHO member states representing a total of 2000 million are affected by dengue. The dengue infection may be asymptomatic or symptomatic. The symptomatic varieties are classical dengue fever, dengue haemorrhagic fever with shock or dengue haemorrhagic fever without shock.

References: www.mayoclinic.org

Causes

Dengue fever is an infectious tropical disease caused by the dengue virus. Dengue fever virus (DENV) is an RNA virus of the family Flaviviridae and exists in four serotypes, namely DEN 1, DEN2, DEN 3 and DEN 4. Infection with one type usually gives lifelong immunity to that type, but only short-term immunity to the others. Subsequent infection with a different type increases the risk of severe complications. Dengue is not transmitted directly from person-to-person. Aedes mosquitoes are the carrier of dengue viruses. This mosquito can be easily distinguished as it is larger in size and have black and white stripes on its body, so it is sometimes called tiger mosquitoes . They usually bite during the day time. They breed in artificial accumulation of fresh water, such as broken bottles and tins, flower pots, coconut shell, tree holes etc. Dengue fever is caused by any one of four dengue viruses spread by Aedes mosquitoes that thrive in and near human lodgings. When a mosquito bites a person infected with a dengue virus, the virus enters the mosquito. When the infected mosquito then bites another person, the virus enters that person's bloodstream. Possible factors for increase in the incidence of Dengue fever are unplanned urban overpopulation leading to inadequate housing and public health systems (water, sewerage and waste management, poor vector control, e.g., stagnant pools of water for mosquito breeding, climate change and viral evolution (increased virus transmission has been linked to El Nino conditions) and increased international travel to endemic areas.

References: www.phac-aspc.gc.ca/lab-bio/res/psds-ftss/msds50e-eng.php www.denguevirusnet.com/history-of-dengue.html www.mayoclinic.org

Symptoms

Usually the symptoms begin four to 10 days after bitten by an infected mosquito. Mild dengue fever causes high fever, rash, and muscle and joint pain. A severe form of dengue fever, also called dengue hemorrhagic fever, can cause severe bleeding, a sudden drop in blood pressure (shock) and death.

The classical symptoms of dengue are sudden onset of fever with chills, intense headache (retro-orbital), severe muscle and backbone pain, vomiting, tastelessness, weakness, dry tongue, constipation, reddish eye, oedoma on face and a characteristic skin rash. The fever is raised upto 102 to 105 degree, lasts for 5-7 days after which the recovery is usually complete.

Due to severe muscle and joint pain associated with this infection, the fever due to this diseases    is commonly known as “Breakbone” fever.

Dengue haemorrhagic fever is the severe form of Dengue fever with any one of the following:

  •  Severe and continuous pain abdomen
  • Bleeding from the nose, mouth and gums or skin bruising
  • Frequent vomiting with or without blood
  • Black stools, like coal tar
  • Excessive thirst (dry mouth)
  • Pale, cold skin
  • Restlessness or sleepiness

Dengue shock syndrome is defined as dengue haemorrhagic fever with weak, rapid pulse, narrow pulse pressure (less than 20 mm of Hg), cold clammy skin and restlessness.

The clinical manifestations are acute onset of continuous fever lasting for 2-7 days, liver enlargement and tenderness, nausea and vomiting, abdominal pain, severe body pain     especially in backbone and joints and bleeding under skin, from nose, gum,  blood in vomitus  and or in stool.

References: 
www.webmd.com
www.medicinenet.com
www.emedicinehealth.com
www.denguevirusnet.com</